The complex perovskite oxide calcium magnesium niobate, CaMg1/3Nb2/3O3 (CMN) is synthesized by a solid-state reaction technique. Dielectric spectroscopy is applied to investigate the electrical properties of CMN in a temperature range from room temperature to 503 K and in a frequency range of 100 Hz-1 MHz. An analysis of the dielectric constant epsilon' and loss tangent tan 6 with frequency is performed assuming a distribution of relaxation times. The low-frequency dielectric dispersion corresponds to the DC electrical conductivity. The frequency dependence of the loss peak is found to obey an Arrhenius law with an activation energy of 1.8 eV. The frequency dependent electrical data are analyzed in the framework of the conductivity and modulus formalisms. Both these formalisms show qualitative similarities in relaxation times. The scaling behaviour of imaginary part of electric modulus M '' suggests that the relaxation describes the same mechanism at various temperatures in CMN. (C) 2007 Elsevier Ltd. All rights reserved.